Memory devices selecting and protecting a possible attacked word line based on the previous refreshed word lines and the relevant methods

Abstract

A memory device and a method for protecting the same are provided. The memory device includes a controller configured to refresh a first word line and a first protected word line during a first refresh cycle in response to a refresh signal, a random number generator configured to receive an address of the first word line and an address of the first protected word line to generate a first number, a counter electrically coupled to the random number generator. The counter is configured to receive the first number as an initial value of the counter, and configured to be turned on in response to the refresh signal. The controller is configured to obtain an address of a second accessed word line being accessed when the counter counts down to zero, and refresh a second protected word line, adjacent to the second accessed word line, during a second refresh cycle.

What is claimed is: 
     
       1. A method for protecting a memory device, wherein the memory device includes a plurality of word lines, the method comprising:
 refreshing a first word line and a first protected word line of the plurality of word lines during a first refresh cycle in response to a refresh signal, wherein the first protected word line is adjacent to a first accessed word line; 
 generating a first number by a random number generator based on an address of the first word line and an address of the first accessed word line; 
 starting counting down from the first number by a counter in response to the refresh signal; 
 obtaining, by a controller, an address of a second accessed word line being accessed when the counter counts to zero; and 
 protecting a second protected word line during a second refresh cycle, wherein the second protected word line is adjacent to the second accessed word line. 
 
     
     
       2. The method of  claim 1 , wherein the first number is represented by a binary sequence having more than 2 bits. 
     
     
       3. The method of  claim 2 , wherein the first number is an 8-bit binary sequence. 
     
     
       4. The method of  claim 1 , wherein the first number is less than a first predetermined number, wherein the first predetermined number is associated with a first time period for accessing a word line and a second time period between the first refresh cycle and the second refresh cycle. 
     
     
       5. The method of  claim 4 , further comprising a number trimmer configured to reset a most significant bit (msb) of the first number when the first number is greater than the first predetermined number. 
     
     
       6. The method of  claim 1 , wherein the random number generator includes a XOR gate. 
     
     
       7. The method of  claim 1 , wherein the address of the first word line and the address of the first accessed word line are each represented by a hexadecimal sequence having 4 bits. 
     
     
       8. The method of  claim 7 , wherein the random number generator is configured to generate the first number based on a first part of the address of the first word line and a first part of the address of the first accessed word line. 
     
     
       9. The method of  claim 1 , further comprising an address register electrically connected to the counter, wherein the address register is configured to obtain and store the address of the first accessed word line that is accessed when the counter counts down to zero. 
     
     
       10. The method of  claim 1 , wherein the controller is further configured to refresh a second word line during the second refresh cycle.